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FEATURE ARTICLES | 2019-07-01

Gear Noise Analysis: Design and Manufacturing Challenges Drive New Solutions for Noise Reduction

Gear noise is among the issues of greatest concern in today's modern gearboxes. Significant research has resulted in the application of enhancements in all phases of gear manufacturing, and the work is ongoing. With the introduction of Electric Vehicles (EV), research and development in this area has surged in recent years. Most importantly, powerful new noise analysis solutions are fast becoming available.

FEATURE ARTICLES | 2019-03-01

Loading Upgrades

The latest advances in gear manufacturing automation all seem to revolve around a common theme: automated loading.

TECHNICAL ARTICLES | 2019-03-01

New Consideration of Non-Metallic Inclusions Calculating Local Tooth Root Load Carrying Capacity of High-Strength, High-Quality Steel Gears

The effects of non-metallic inclusions in steel matrix on tooth root strength based on theoretical approach of Murakami.

FEATURE ARTICLES | 2019-01-01

The Growth of Australian Regenerative Load Testing

Historically, gearbox original equipment manufacturers (OEMs) and repair organizations have tended to offer their customers no-load, full speed (spin) tests as a standard performance test. If a load test was specified, the supplier would probably offer a locked torque back-to-back simulated load test, which requires a large investment in tooling to connect shafts of the test and slave gearboxes.

GEAR TALK WITH CHUCK | 2018-12-06

Out With the Old

No technology ...

TECHNICAL ARTICLES | 2018-11-01

The Influence of a Grinding Notch on the Gear Bending Strength Rating

To achieve the requested quality, most gears today are ground. The usual grinding process includes treating the gear flank but disengaging before reaching the root rounding area. If the gear is premanufactured with a tool without protuberance, then at the position where the grinding tool retracts from the flank a grinding notch in the tooth root area is produced. Such a notch may increase the bending stresses in the root area, thus reducing the strength rating.

TECHNICAL ARTICLES | 2018-11-01

Full Contact Analysis vs. Standard Load Capacity Calculation for Cylindrical Gears

In this paper local tooth contact analysis and standard calculation are used to determine the load capacity for the failure modes pitting, tooth root breakage, micropitting, and tooth flank fracture; analogies and differences between both approaches are shown. An example gearset is introduced to show the optimization potential that arises from using a combination of both methods. Difficulties in combining local approaches with standard methods are indicated. The example calculation demonstrates a valid possibility to optimize the gear design by using local tooth contact analysis while satisfying the requirement of documenting the load carrying capacity by standard calculations.

TECHNICAL ARTICLES | 2018-08-01

Influences of the Residual Stress Condition on the Load-Carrying Capacity of Case-Hardened Gears

Highly loaded gears are usually casehardened to fulfill the high demands on the load-carrying capacity. Several factors, such as material, heat treatment, or macro and micro geometry, can influence the load-carrying capacity. Furthermore, the residual stress condition also significantly influences load-carrying capacity. The residual stress state results from heat treatment and can be further modified by manufacturing processes post heat treatment, e.g. grinding or shot peening.

GEAR TALK WITH CHUCK | 2018-05-17

Computer Games

You kids are spoiled! Back in my day it took at least a day to see the results of computer modeling, longer if the courier dropped the box of input...

GEAR TALK WITH CHUCK | 2018-05-08

Making Things Work

There is an old saying that if the only tool you have is a hammer, everything looks like a nail. Imagine that you are tasked by your employer to de...

GEAR TALK WITH CHUCK | 2018-01-16

The Company You Keep

Learning about gears is much easier in a group setting. Anyone who suffered through a tough high school or university class without study buddies w...

TECHNICAL ARTICLES | 2017-11-01

Influence of the Defect Size on the Tooth Root Load Carrying Capacity

The objective of this work is to introduce a method for the calculation of the tooth root load carrying capacity for gears, under consideration of the influence of the defect size on the endurance fatigue strength of the tooth root. The theoretical basis of this method is presented in this paper as well as the validation in running tests of helical and beveloid gears with different material batches, regarding the size distribution of inclusions. The torque level for a 50 percent failure probability of the gears is evaluated on the test rig and then compared to the results of the simulation. The simulative method allows for a performance of the staircase method that is usually performed physically in the back-to-back tests for endurance strength, as the statistical influence of the material properties is considered in the calculation model. The comparison between simulation and tests shows a high level of accordance.

TECHNICAL ARTICLES | 2017-08-01

Determination of Maximum Loads for Drivetrain Components in Thrusters Using Flexible Multibody-System Models

The usage of modern thrusters allows combining the functions of the drive and the ship rudder in one unit, which are separated in conventional ship propulsion systems. The horizontally oriented propeller is supported in a vertically rotatable nacelle that is mounted underneath the ship's hull. The propeller can directly or indirectly be driven by an electric motor or combustion engine. Direct drive requires the installation of a low-speed electric motor in the nacelle. This present paper concentrates on indirect drives where the driving torque is transferred by bevel gear stages and shafts from the motor to the propeller.

TECHNICAL ARTICLES | 2017-05-01

Inclusion-Based Bending Strength Calculation of Gears

Reduced component weight and ever-increasing power density require a gear design on the border area of material capacity. In order to exploit the potential offered by modern construction materials, calculation methods for component strength must rely on a deeper understanding of fracture and material mechanics in contrast to empirical-analytical approaches.

TECHNICAL ARTICLES | 2016-09-01

Increased Tooth Bending Strength and Pitting Load Capacity of Fine-Module Gears

The common calculation methods according to DIN 3990 and ISO 6336 are based on a comparison of occurring stress and allowable stress. The influence of gear size on the load-carrying capacity is considered with the size factors YX (tooth root bending) and ZX (pitting), but there are further influences, which should be considered. In the following, major influences of gear size on the load factors as well as on the permissible tooth root bending and contact stress will be discussed.

TECHNICAL ARTICLES | 2016-01-01

Influences on Failure Modes and Load-Carrying Capacity of Grease-Lubricated Gears

In order to properly select a grease for a particular application, a sound knowledge of the influence of different grease components and operating conditions on the lubrication supply mechanism and on different failure modes is of great benefit.

TECHNICAL ARTICLES | 2015-06-01

Optimal Modifications on Helical Gears for Good Load Distribution and Minimal Wear

Helical gear teeth are affected by cratering wear — particularly in the regions of low oil film thicknesses, high flank pressures and high sliding speeds. The greatest wear occurs on the pinion — in the area of negative specific sliding. Here the tooth tip radius of the driven gear makes contact with the flank of the driving gear with maximum sliding speed and pressure.

ASK THE EXPERT | 2015-03-01

Calculating Face Load Distribution Factor

How should we consider random helix angle errors fHβ and housing machining errors when calculating KHβ? What is a reasonable approach?

TECHNICAL ARTICLES | 2014-06-01

Calculation of Tooth Root Load Carrying Capacity of Beveloid Gears

In this paper, two developed methods of tooth root load carrying capacity calculations for beveloid gears with parallel axes are presented, in part utilizing WZL software GearGenerator and ZaKo3D. One method calculates the tooth root load-carrying capacity in an FE-based approach. For the other, analytic formulas are employed to calculate the tooth root load-carrying capacity of beveloid gears. To conclude, both methods are applied to a test gear. The methods are compared both to each other and to other tests on beveloid gears with parallel axes in test bench trials.

TECHNICAL ARTICLES | 2014-05-01

Load Distribution Analysis of Spline Joints

A finite elements-based contact model is developed to predict load distribution along the spline joint interfaces; effects of spline misalignment are investigated along with intentional lead crowning of the contacting surfaces. The effects of manufacturing tooth indexing error on spline load distributions are demonstrated by using the proposed model.

TECHNICAL ARTICLES | 2014-05-01

Application and Improvement of Face Load Factor Determination Based on AGMA 927

The face load factor is one of the most important items for a gear strength calculation. Current standards propose formulae for face load factor, but they are not always appropriate. AGMA 927 proposes a simpler and quicker algorithm that doesn't require a contact analysis calculation. This paper explains how this algorithm can be applied for gear rating procedures.

TECHNICAL ARTICLES | 2013-06-01

New Methods for the Calculation of the Load Capacity of Bevel and Hypoid Gears

Flank breakage is common in a number of cylindrical and bevel gear applications. This paper introduces a relevant, physically based calculation method to evaluate flank breakage risk vs. pitting risk. Verification of this new method through testing is demonstrably shown.

TECHNICAL ARTICLES | 2013-06-01

Tooth Root Optimization of Powder Metal Gears - Reducing Stress from Bending and Transient Loads

This paper will provide examples of stress levels from conventional root design using a hob and stress levels using an optimized root design that is now possible with PM manufacturing. The paper will also investigate how PM can reduce stresses in the root from transient loads generated by abusive driving.

TECHNICAL ARTICLES | 2012-06-01

FZG Rig-Based Testing of Flank Load-Carrying Capacity Internal Gears

Micropitting, pitting and wear are typical gear failure modes that can occur on the flanks of slowly operated and highly stressed internal gears. However, the calculation methods for the flank load-carrying capacity have mainly been established on the basis of experimental investigations of external gears. This paper describes the design and functionality of the newly developed test rigs for internal gears and shows basic results of the theoretical studies. It furthermore presents basic examples of experimental test results.

TECHNICAL ARTICLES | 2011-11-01

Load-Sharing Model for Polymer Cylindrical Gears

This paper presents an original method to compute the loaded mechanical behavior of polymer gears. Polymer gears can be used without lubricant, have quieter mesh, are more resistant to corrosion, and are lighter in weight. Therefore their application fields are continually increasing. Nevertheless, the mechanical behavior of polymer materials is very complex because it depends on time, history of displacement and temperature. In addition, for several polymers, humidity is another factor to be taken into account. The particular case of polyamide 6.6 is studied in this paper.

TECHNICAL ARTICLES | 2011-10-01

Comparison of Test Rig and Field Measurement Results on Gearboxes for Wind Turbines

This article describes some of the most important tests for prototypes conducted at Winergy AG during the product development process. It will demonstrate that the measurement results on the test rig for load distribution are in accordance with the turbine measurements.

TECHNICAL ARTICLES | 2011-09-01

Size and Material Influence on the Tooth Root, Pitting, Scuffing and Wear Load-Carrying Capacity of Fine-Module Gears

In this study, limiting values for the load-carrying-capacity of fine-module gears within the module range 0.3–1.0 mm were determined and evaluated by comprehensive, experimental investigations that employed technical, manufacturing and material influence parameters.

TECHNICAL ARTICLES | 2011-09-01

Analysis of Load Distribution in Planet Gear Bearings

In epicyclic gear sets designed for aeronautical applications, planet gears are generally supported by spherical roller bearings with the bearing outer race integral to the gear hub. This article presents a new method to compute roller load distribution in such bearings where the outer ring can’t be considered rigid.

TECHNICAL ARTICLES | 2011-05-01

Flank Load Carrying Capacity and Power Loss Reduction by Minimized Lubrication

The objective of this study was to investigate the limits concerning possible reduction of lubricant quantity in gears that could be tolerated without detrimental effects on their load carrying capacity.

TECHNICAL ARTICLES | 2009-07-01

The Effect of Manufaturing Microgeometry Variations on the Load Distribution Factor and on Gear Contact and Root Stresses

Traditionally, gear rating procedures consider manufacturing accuracy in the application of the dynamic factor, but only indirectly through the load distribution are such errors in the calculation of stresses used in the durability and gear strength equations. This paper discusses how accuracy affects the calculation of stresses and then uses both statistical design of experiments and Monte Carlo simulation techniques to quantify the effects of different manufacturing and assembly errors on root and contact stresses.

TECHNICAL ARTICLES | 2009-06-01

The Effect of Start-Up Load Conditions on Gearbox Performance and Life Failure Analysis, With Supporting Case Study

If a gear system is run continuously for long periods of time—or if the starting loads are very low and within the normal operating spectrum—the effect of the start-up conditions may often be insignificant in the determination of the life of the gear system. Conversely, if the starting load is significantly higher than any of the normal operating conditions, and the gear system is started and stopped frequently, the start-up load may, depending on its magnitude and frequency, actually be the overriding, limiting design condition.

TECHNICAL ARTICLES | 2008-11-01

An Investigation of the Influence of Shaft Misalignment on Bending Stresses of Helical Gears with Lead Crown

In this study, the combined influence of shaft misalignments and gear lead crown on load distribution and tooth bending stresses is investigated. Upon conclusion, the experimental results are correlated with predictions of a gear load distribution model, and recommendations are provided for optimal lead crown in a given misalignment condition.

TECHNICAL ARTICLES | 2008-08-01

Influence of Grinding Burn on Pitting Capacity

This paper intends to determine the load-carrying capacity of thermally damaged parts under rolling stress. Since inspection using real gears is problematic, rollers are chosen as an acceptable substitute. The examined scope of thermal damage from hard finishing extends from undamaged, best-case parts to a rehardening zone as the worst case. Also, two degrees of a tempered zone have been examined.

TECHNICAL ARTICLES | 2008-05-01

Pitting Load Capacity of Helical Gears

Influences of Load Distribution and Tooth Flank Modifications as Considered in a New, DIN/ISO-Compatible Calculation Method

TECHNICAL ARTICLES | 2007-07-01

Experience with Large, High-Speed Load Gears

The main theme of this article is high-capacity, high-speed load gears in a power transmission range between 35 MW and 100 MW for generators and turbo-compressors driven by gas or steam turbines.

TECHNICAL ARTICLES | 2007-05-01

Thermal Behavior of Helical Gears

An experimental effort has been conducted on an aerospace-quality helical gear train to investigate the thermal behavior of the gear system as many important operational conditions were varied.

TECHNICAL ARTICLES | 2006-07-01

Generating Interchangeable 20-Degree Spur Gear Sets with Circular Fillets to Increase Load Carrying Capacity

This article presents a new spur gear 20-degree design that works interchangeably with the standard 20-degree system and achieves increased tooth bending strength and hence load carrying capacity.

TECHNICAL ARTICLES | 2004-09-01

Surface Damage Caused by Gear Profile Grinding and its Effects on Flank Load Carrying Capacity

Instances of damage to discontinuous form ground and surface-hardened gears, especially of large scale, have recently increased. This may be attributed partly to a faulty grinding process with negative effects on the surface zones and the surface properties.

TECHNICAL ARTICLES | 2004-07-01

Load Carrying Capacity of Screw Helical Gears with Steel Pinions and Plastic Wheels

There is an increasing significance of screw helical and worm gears that combine use of steel and plastics. This is shown by diverse and continuously rising use in the automotive and household appliance industries. The increasing requirements for such gears can be explained by the advantageous qualities of such a material combination in comparison with that of the traditional steel/bronze pairing.

TECHNICAL ARTICLES | 2003-09-01

Local 3-D Flank Form Optimizations for Bevel Gears

Optimizing the running behavior of bevel and hypoid gears means improving both noise behavior and load carrying capacity. Since load deflections change the relative position of pinion and ring gear, the position of the contact pattern will depend on the torque. Different contact positions require local 3-D flank form optimizations for improving a gear set.

TECHNICAL ARTICLES | 2003-03-01

Determination and Optimization of the Contact Pattern of Worm Gears

The load capacity of worm gears is mainly influenced by the size and the position of the contact pattern.

TECHNICAL ARTICLES | 2000-11-01

Parallel Axis Gear Grinding: Theory & Application

The goal of gear drive design is to transit power and motion with constant angular velocity. Current trends in gear drive design require greater load carrying capacity and increased service life in smaller, quieter, more efficient gearboxes. Generally, these goals are met by specifying more accurate gears. This, combined with the availability of user-friendly CNC gear grinding equipment, has increased the use of ground gears.

TECHNICAL ARTICLES | 2000-05-01

The Design and Testing of a Low Noise Marine Gear

This article offers an overview of the practical design of a naval gear for combined diesel or gas turbine propulsion (CODOG type). The vibration performance of the gear is tested in a back-to-back test. The gear presented is a low noise design for the Royal Dutch Navy's LCF Frigate. The design aspects for low noise operation were incorporated into the overall gear system design. Therefore, special attention was paid to all the parameters that could influence the noise and vibration performance of the gearbox. These design aspects, such as tooth corrections, tooth loading, gear layout, balance, lubrication and resilient mounting, will be discussed.

TECHNICAL ARTICLES | 1994-07-01

Effect of Extended Tooth Contact on the Modeling of Spur Gear Transmissions

In some gear dynamic models, the effect of tooth flexibility is ignored when the model determines which pairs of teeth are in contact. Deflection of loaded teeth is not introduced until the equations of motion are solved. This means the zone of tooth contact and average tooth meshing stiffness are underestimated, and the individual tooth load is overstated, especially for heavily loaded gears. This article compares the static transmission error and dynamic load of heavily loaded, low-contact-ratio spur gears when the effect of tooth flexibility has been considered and when it has been ignored. Neglecting the effect yields an underestimate of resonance speeds and an overestimate of the dynamic load.

TECHNICAL ARTICLES | 1993-11-01

CBN Gear Grinding - A Way to Higher Load Capacity

Because of the better thermal conductivity of CBN abrasives compared to that of conventional aluminum oxide wheels, CBN grinding process, which induces residual compressive stresses into the component, and possibly improves the subsequent stress behavior. This thesis is the subject of much discussion. In particular, recent Japanese publications claim great advantages for the process with regard to an increased component load capacity, but do not provide further details regarding the technology, test procedures or components investigated. This situation needs clarification, and for the this reason the effect of the CBN grinding material on the wear behavior and tooth face load capacity of continuously generated ground gears was further investigated.

TECHNICAL ARTICLES | 1990-05-01

Dynamic Loads in Parallel Shaft Transmissions - Part 2

Solutions to the governing equations of a spur gear transmission model, developed in a previous article are presented. Factors affecting the dynamic load are identified. It is found that the dynamic load increases with operating speed up to a system natural frequency. At operating speeds beyond the natural frequency the dynamic load decreases dramatically. Also, it is found that the transmitted load and shaft inertia have little effect upon the total dynamic load. Damping and friction decrease the dynamic load. Finally, tooth stiffness has a significant effect upon dynamic loadings the higher the stiffness, the lower the dynamic loading. Also, the higher the stiffness, the higher the rotating speed required for peak dynamic response.

TECHNICAL ARTICLES | 1990-05-01

Comparative Load Capacity Evaluation of CBN-Finished Gears

Cubic boron nitride (CBN) finishing of carburized gearing has been shown to have certain economic and geometric advantages and, as a result, it has been applied to a wide variety of precision gears in many different applications. In critical applications such as aerospace drive systems, however, any new process must be carefully evaluated before it is used in a production application. Because of the advantages associated with this process, a test program was instituted to evaluate the load capacity of aerospace-quality gears finished by the CBN process as compared to geometrically identical gears finished by conventional grinding processes. This article presents a brief description of the CBN process, its advantages in an aerospace application, and the results of an extensive test program conducted by Boeing Helicopters (BH) aimed at an evaluation of the effects of this process on the scoring, surface durability, and bending fatigue properties of spur gears. In addition, the results of an x-ray diffraction study to determine the surface and subsurface residual stress distributions of both shot-peened and nonshot-peened CBN-ground gears as compared to similar conventionally ground gears are also presented.

TECHNICAL ARTICLES | 1990-03-01

Dynamic Loads in Parallel Shaft Transmissions Part 1

Recently, there has been increased interest in the dynamic effects in gear systems. This interest is stimulated by demands for stronger, higher speed, improved performance, and longer-lived systems. This in turn had stimulated numerous research efforts directed toward understanding gear dynamic phenomena. However, many aspects of gear dynamics are still not satisfactorily understood.

TECHNICAL ARTICLES | 1990-01-01

Application of Miner's Rule to Industrial Gear Drives

We need a method to analyze cumulative fatigue damage to specify and to design gear drives which will operate under varying load. Since load is seldom constant, most applications need this analysis.

TECHNICAL ARTICLES | 1989-03-01

Predicted Effect of Dynamic Load on Pitting Fatigue Life for Low-Contact-Ratio Spur Gears

How dynamic load affects the pitting fatigue life of external spur gears was predicted by using NASA computer program TELSGE. TELSGE was modified to include an improved gear tooth stiffness model, a stiffness-dynamic load iteration scheme and a pitting-fatigue-life prediction analysis for a gear mesh. The analysis used the NASA gear life model developed by Coy, methods of probability and statistics and gear tooth dynamic loads to predict life. In general, gear life predictions based on dynamic loads differed significantly from those based on static loads, with the predictions being strongly influenced by the maximum dynamic load during contact.

TECHNICAL ARTICLES | 1987-05-01

Influence of Geometrical Parameters on the Gear Scuffing Criterion - Part 2

In ParI 1 several scuffing (scoring) criteria were shown ultimately to converge into one criterion, the original flash temperature criterion according to Blok. In Part 2 it will be shown that all geometric influences may be concentrated in one factor dependent on only four independent parameters, of which the gear ratio, the number of teeth of the pinion, and the addendum modification coefficient of the pinion are significant.

TECHNICAL ARTICLES | 1987-03-01

Influence of Geometrical Parameters on the Gear Scuffing Criterion - Part I

The load capacity rating of gears had its beginning in the 18th century at Leiden University when Prof. Pieter van Musschenbroek systematically tested the wooden teeth of windmill gears, applying the bending strength formula published by Galilei one century earlier. In the next centuries several scientists improved or extended the formula, and recently a Draft International Standard could be presented.

TECHNICAL ARTICLES | 1987-01-01

Improvement in Load Capacity of Crossed Helical Gears

Crossed helical gear sets are used to transmit power and motion between non-intersecting and non-parallel axes. Both of the gears that mesh with each other are involute helical gears, and a point contact is made between them. They can stand a small change in the center distance and the shaft angle without any impairment in the accuracy of transmitting motion.

TECHNICAL ARTICLES | 1986-09-01

Practical Analysis of Highly-Loaded Gears by Using the Modified-Scoring Index Calculation Method

The power of high speed gears for use in the petrochemical industry and power stations is always increasing. Today gears with ratings of up to 70,000kW are already in service. For such gears, the failure mode of scoring can become the limiting constraint. The validity of an analytical method to predict scoring resistance is, therefore, becoming increasingly important.

TECHNICAL ARTICLES | 1986-03-01

Controlling Tooth Loads In Helical Gears

Helical gears can drive either nonparallel or parallel shafts. When these gears are used with nonparallel shafts, the contact is a point, and the design and manufacturing requirements are less critical than for gears driving parallel shafts.

TECHNICAL ARTICLES | 1986-03-01

A Computer Solution for the Dynamic Load, Lubricant Film Thickness, and Surface Temperatures in Spiral-Bevel Gears

Spiral-bevel gears, found in many machine tools, automobile rear-axle drives, and helicopter transmissions, are important elements for transmitting power.

TECHNICAL ARTICLES | 1985-07-01

Influence of Relative Displacements Between Pinion and Gear on Tooth Root Stresses of Spiral Bevel Gears

The manufacturing quality of spiral bevel gears has achieved a very high standard. Nevertheless, the understanding of the real stress conditions and the influences. of certain parameters is not satisfactory.

TECHNICAL ARTICLES | 1985-07-01

Longitudinal Load Distribution Factor of Helical Gears

The contact lines of a pair of helical gears move diagonally on the engaged tooth faces and their lengths consequently vary with the rotation of the gears.

TECHNICAL ARTICLES | 1984-10-01

Scoring Load Capacity of Gears Lubricated with EP-Oils

The Integral Temperature Method for the evaluation of the scoring load capacity of gears is described. All necessary equations for the practical application are presented. The limit scoring temperature for any oil can be obtained from a gear scoring test.